AS/400

AS/400. The IBM AS/400 is a family of midrange computers introduced in 1988, designed for small to medium-sized businesses and departmental use in larger enterprises. It was renowned for its integration of hardware and software, object-based architecture, and exceptional backward compatibility. The platform evolved through several rebrandings, ultimately becoming part of the IBM Power Systems family, while retaining its core operating system, now known as IBM i.

History and development

The development of the AS/400 was led by a team under Frank G. Soltis, building upon concepts from the earlier IBM System/38. Announced on June 21, 1988, it was positioned as a successor to both the System/38 and the IBM System/36, aiming to consolidate IBM's midrange offerings. The project, known internally as "Silverlake," was developed in Rochester, Minnesota, and involved a massive collaborative effort across IBM's divisions. A key strategic decision was to ensure compatibility with software from its predecessors, which proved crucial for its market acceptance. Over its lifetime, the platform was rebranded several times, first to IBM iSeries in 2000, then to IBM System i in 2006, before its hardware was merged with the IBM System p line to create the unified IBM Power Systems in 2008.

Architecture and technical features

The architecture of the AS/400 was fundamentally object-based, with all system resources, including programs, data files, and user profiles, treated as objects managed by the Machine Interface (MI). This abstraction layer between the hardware and the OS/400 operating system was a defining innovation, ensuring application independence from the underlying hardware. The system featured a unified database architecture with DB2 for i integrated directly into the operating system. Its Technology Independent Machine Interface allowed applications compiled on the original CISC-based systems to run without modification on later POWER and PowerPC-based models. Other notable features included single-level storage, which presented disk and memory as a single address space, and a robust integrated security model.

Operating system and software

The native operating system was OS/400, which provided a completely integrated environment including the DB2 for i database, TCP/IP networking, and system management tools. A key component was the Control Language (CL), used for system control and automation. For application development, primary languages included RPG, COBOL, C, and C++, with the IBM Rational suite of tools later becoming prominent. The system could also host other operating systems; with optional partitions, it could run AIX, Linux, or Microsoft Windows via Integrated xSeries Server cards. A vast ecosystem of third-party business applications, particularly for industries like manufacturing, distribution, and banking, was developed for the platform.

Market impact and evolution

The AS/400 achieved significant commercial success, with over half a million systems sold worldwide, solidifying IBM's dominance in the midrange business computing market. It became a backbone for critical applications in sectors such as finance, healthcare, and retail, prized for its reliability and low total cost of ownership. Its evolution through rebranding to IBM iSeries and IBM System i reflected IBM's e-business and On Demand computing initiatives. The final architectural merger with IBM Power Systems allowed the IBM i operating system to run on the latest POWER processor technology, ensuring the platform's continued relevance in modern cloud computing and analytics environments.

Hardware models and specifications

The original AS/400 models, such as the B10, B20, B30, B40, B50, B60, and B70, were based on a 48-bit CISC processor. Subsequent generations transitioned to IMPI and then to PowerPC and POWER RISC processors, offering dramatic performance improvements. The hardware range expanded from compact deskside units to large rack-mounted and tower systems in the later iSeries and System i generations. Key specifications evolved to include advanced features like dynamic logical partitioning (LPAR), POWER5 and POWER6 processors, and integration with IBM System Storage SAN solutions. The unified IBM Power Systems models, such as the Power 520 and Power 720, continued to support the IBM i operating system alongside AIX and Linux.

Category:IBM midrange computers Category:Computer-related introductions in 1988